[PATCH v17 16/20] KVM: arm64: CCA: Provide register list for unfinalized RECs

[Suzuki K Poulose <suzuki.poulose@arm.com>]

From: Jean-Philippe Brucker <jean-philippe@linaro.org>

KVM_GET_REG_LIST should not be called before SVE is finalized. The ioctl
handler currently returns -EPERM in this case. But because it uses
kvm_arm_vcpu_is_finalized(), it now also rejects the call for
unfinalized REC even though finalizing the REC can only be done late,
after Realm descriptor creation.

Move the check to copy_sve_reg_indices(). One adverse side effect of
this change is that a KVM_GET_REG_LIST call that only probes for the
array size will now succeed even if SVE is not finalized, but that seems
harmless since the following KVM_GET_REG_LIST with the full array will
fail.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Steven Price <steven.price@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 arch/arm64/kvm/arm.c   | 14 +++++++++++++-
 arch/arm64/kvm/guest.c | 10 +++++-----
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index fbb4d6651ab51..3fe5a4f77738e 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1980,6 +1980,18 @@ static int kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 	return __kvm_arm_vcpu_set_events(vcpu, events);
 }
 
+/*
+ * Realm VCPUs can be finalized after the Realm descriptor is created.
+ * Allow the register list for RECs before the VCPUs are finalized, but
+ * after the SVE is finalized.
+ */
+static bool kvm_arm_vcpu_reg_list_allowed(struct kvm_vcpu *vcpu)
+{
+	if (kvm_arm_vcpu_is_finalized(vcpu))
+		return true;
+	return vcpu_is_rec(vcpu);
+}
+
 long kvm_arch_vcpu_ioctl(struct file *filp,
 			 unsigned int ioctl, unsigned long arg)
 {
@@ -2035,7 +2047,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 			break;
 
 		r = -EPERM;
-		if (!kvm_arm_vcpu_is_finalized(vcpu))
+		if (!kvm_arm_vcpu_reg_list_allowed(vcpu))
 			break;
 
 		r = -EFAULT;
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index b01d6622b8720..c3ca369882273 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -598,8 +598,8 @@ static unsigned long num_sve_regs(const struct kvm_vcpu *vcpu)
 	if (!vcpu_has_sve(vcpu))
 		return 0;
 
-	/* Policed by KVM_GET_REG_LIST: */
-	WARN_ON(!kvm_arm_vcpu_sve_finalized(vcpu));
+	if (!kvm_arm_vcpu_sve_finalized(vcpu))
+		return 1; /* KVM_REG_ARM64_SVE_VLS */
 
 	return slices * (SVE_NUM_PREGS + SVE_NUM_ZREGS + 1 /* FFR */)
 		+ 1; /* KVM_REG_ARM64_SVE_VLS */
@@ -616,9 +616,6 @@ static int copy_sve_reg_indices(const struct kvm_vcpu *vcpu,
 	if (!vcpu_has_sve(vcpu))
 		return 0;
 
-	/* Policed by KVM_GET_REG_LIST: */
-	WARN_ON(!kvm_arm_vcpu_sve_finalized(vcpu));
-
 	/*
 	 * Enumerate this first, so that userspace can save/restore in
 	 * the order reported by KVM_GET_REG_LIST:
@@ -628,6 +625,9 @@ static int copy_sve_reg_indices(const struct kvm_vcpu *vcpu,
 		return -EFAULT;
 	++num_regs;
 
+	if (!kvm_arm_vcpu_sve_finalized(vcpu))
+		return num_regs;
+
 	for (i = 0; i < slices; i++) {
 		for (n = 0; n < SVE_NUM_ZREGS; n++) {
 			reg = KVM_REG_ARM64_SVE_ZREG(n, i);
-- 
2.43.0